chore: avoid multiple calls to onclose when terminating

Author: johnnyasantoss

src/client/stdio.ts

@@ -134,7 +134,6 @@ export class StdioClientTransport implements Transport {
             this._process.on('error', error => {
                 if (error.name === 'AbortError') {
                     // Expected when close() is called.
-                    this.onclose?.();
                     return;
                 }
 

src/integration-tests/process-cleanup.test.ts

@@ -1,3 +1,5 @@
+import { Client } from '../client/index.js';
+import { StdioClientTransport } from '../client/stdio.js';
 import { Server } from '../server/index.js';
 import { StdioServerTransport } from '../server/stdio.js';
 
@@ -25,4 +27,30 @@ describe('Process cleanup', () => {
         // The test runner will fail if the process hangs
         expect(true).toBe(true);
     });
+
+    it('onclose should be called exactly once', async () => {
+        const client = new Client({
+            name: 'test-client',
+            version: '1.0.0'
+        });
+
+        const transport = new StdioClientTransport({
+            command: process.argv0,
+            args: ['test-server.js'],
+            cwd: __dirname
+        });
+
+        let onCloseWasCalled = 0;
+        client.onclose = () => {
+            onCloseWasCalled++;
+        };
+
+        await client.connect(transport);
+        await client.close();
+
+        // A short delay to allow the close event to propagate
+        await new Promise(resolve => setTimeout(resolve, 50));
+
+        expect(onCloseWasCalled).toBe(1);
+    });
 });

src/integration-tests/test-server.js

@@ -0,0 +1,11 @@
+import { McpServer } from "../../dist/esm/server/mcp.js";
+import { StdioServerTransport } from "../../dist/esm/server/stdio.js";
+
+const transport = new StdioServerTransport();
+
+const server = new McpServer({
+  name: "test-server",
+  version: "1.0.0",
+});
+
+await server.connect(transport);